The present invention is directed to the separation of low molecular weight organic contaminants from aqueous environments such as ponds, streams, lakes, rivers, estuaries or the like, or biological extracts, into organic solvents, using substantially non-porous polymers to enclose lipids in the dialysis of such contaminants. More specifically it includes the use of non-porous polymeric films as contaminants or impurities from biogenic extracts or liquids into organic solvent.
Non-porous polymeric membranes are so-called because the can be generally considered non-porous but are known to have pseudo-pores or transport corridors in the range of 5 to 10 .ANG. in diameter They are stable in a variety of organic solvents and biogenic extracts, and are ideal for the dialytic separation of organic contaminant residues because most toxic organic contaminants have cross-sectional diameters of less than 10 .ANG..
As can be seen by reference to the following U.S. Pat. Nos. 3,339,341; 3,463,728; 3,567,632; 3,951,789; and 3,956,112; the prior art is replete with myriad and diverse processes for separating a solute from a solvent and for extracting solutes via membranous diffusion.
While all of the aforementioned prior art constructions are more than adequate for the basic purpose and function for which they have been specifically designed, these constructions function poorly in the separation of low molecular weight organic contaminants from aqueous environments or the removal of contaminants from biogenic extracts into organic solvents.
Existing techniques applied to the extraction of organic contaminants from an aqueous environment directly into a low molecular weight organic solvent have been relatively unsuccessful. The low molecular weight of most organic solvents used in this context requires the use of substantially non-porous polymeric membranes to enclose these solvents in order to prevent the solvent from escaping its enclosure through the pores of the membrane. Even so, a significant amount of solvent is lost over time in dialytic or monitoring procedures, which prohibits contaminant residues in the enclosed solvent from reaching their equilibrium concentrations.
In addition, common methods of separating organic contaminants from lipids or biogenic extracts are often inadequate for removing significant but low concentrations of the contaminants from lipids or biogenic extracts. These methods include destructive acid or base hydrolysis, adsorptive chromatography, gel permeation or size exclusion chromatography and liquid-liquid partitioning. A major drawback of these methods is the large solvent requirement for the chromatographic techniques and their relatively low lipid capacity, as well as the failure of liquid-liquid partitioning to prevent large neutral lipids from carrying over to the nonpolar liquid phase with the contaminants of interest.
As a consequence of the foregoing situation, there has existed a long-standing need for a process or processes that can accomplish the of low molecular weight organic contaminants or impurities from aqueous environments or biological extracts into organic solvent. The provision of such a construction is a stated objective of the present invention.